You can see pages in Dublin, that show the Dark Ages weren't so dark. There's also a movie. An account of Viking plunder 1000 years ago:

Quote:

The chief relic of the Western World, was wickedly stolen during the night from the western sacristy of the great stone church at Cenannas on account of its wrought shrine". The manuscript was recovered a few months later—minus its golden and bejewelled cover—"under a sod."

There's your lost Macguffin. But although gold relics are sometimes found in the bog, the cover is probably long gone.